One way to do this (at least in MtG) is to play “cheap” formats: only use so-called “common” cards (examples: https://www.mtggoldfish.com/metagame/pauper#paper). Only use a certain set or a number of sets. In DnD, there’s the concept of “session 0” where the players determine how they’re going to play the game - it helps for players in card games to have a similar rules for power level and expectation.

And it’s pretty well known in the card game community that if you’re looking for cards, you should NEVER buy packs. Buy your singles, and save your money.